Role of flavonoids and vitamins in cancer.

Flavonoids are naturally occurring polyphenolic plant compounds that are capable of inhibiting histamine and cytokine release from several cells. Many studies suggest that flavonoids are anticancer agents with an apoptotic effect on tumor cells. Studies with animal tumour models have found vitamin deficiency to enhance susceptibility to chemical carcinogenesis and large doses of anti-oxidant vitamins and flavonoids to inhibit carcinogenesis. In some studies flavonoids and/or vitamins were found to reduce the predisposition to develop tumours in animals and humans. In conclusion, in this review we describe the role of flavonoids and vitamins in cancer.

Relevance of plant lectins in human cell biology and immunology.

Protein-carbohydrate interactions are used for intercellular communication. Mammalian cells are known to bear a variety of glycoconjugates. Lectins, first discovered in plants, are proteins which can specifically bind carbohydrates. Given the high affinity of plant lectins for carbohydrates, they have always been important as molecular tools in the identification, purification and stimulation of specific glycoproteins on human cells. Lectins have provided important clues to the repertoire of carbohydrate structures in animal cells. The discovery of plant lectins gave a great impulse to modern glycobiology. They represent important biochemical reagents for numerous applications in the biomedical field and in research. Sequence determinations and structural characterization helped to understand the mechanism of action in many biologic systems. Plant lectins have been fundamental in human immunological studies because some of them are mitogenic/activating to lymphocytes. Understanding the molecular basis of lectin-carbohydrate interactions and of the intracellular signalling evoked holds promise for the design of novel drugs for the treatment of infectious, inflammatory and malignant diseases. It may also be of help for the structural and functional investigation of glycoconjugates and their changes during physiological and pathological processes.

Inhibitory effects of cadmium on peripheral blood mononuclear cell proliferation and cytokine release are reversed by zinc and selenium salts.

Zinc (Zn) and selenium (Se) exert regulatory activities on immune functions, while cadmium (Cd) is an immunotoxic agent. The object of this study was to detect effects of 10(-4), 10(-5), and 10(-6) M Cd sulphate, Zn sulphate, and sodium selenite, and their combinations on human peripheral blood mononuclear cell (PBMC) proliferation and IFN-gamma and TNF-alpha production. Only 10(-5) M Zn sulphate significantly enhanced spontaneous PBMC proliferation, which was unaffected by the other salts. At 10(-4) and 10(-5) M, Cd sulphate exerted a dose-response inhibitory action on phytohemagglutinin- (PHA-) stimulated PBMC proliferation and cytokine release, while 10(-4) M and 10(-5) M Zn sulphate and 10(-5) M sodium selenite induced a stimulatory effect on both proliferation and cytokine release; 10(-4) M sodium selenite enhanced only the PBMC proliferation; at 10(-6) M, none of the salts changed the PHA-stimulated immune activity. Moreover, 10(-4) and 10(-5) M Zn and 10(-5) M Se strongly upregulated IFN-gamma (a Th1 cytokine) release, even in presence of 10(-5) M Cd, and reduced the inhibitory effects of Cd on PBMC proliferation and TNF-alpha release. This study confirms that Zn and Se both strongly enhance cytokine release induced by mitogenic stimulation, showing also that Zn acts with a broader range of concentrations than Se. This suggests that dietary excess of Se may not have beneficial effects.